The invention relates to an apparatus for providing a supply voltage for operating an electric device of a vehicle, particularly for operating an electric motor of the vehicle, for driving the vehicle. The invention additionally relates to an electrically driven vehicle having such an apparatus. In addition, the invention relates to a method for providing a supply voltage for operating an electric device for a vehicle, particularly for operating an electric motor of the vehicle, that is used for driving the vehicle.
As a result of increased environmental concerns and the increasing scarcity of raw materials for producing fuels for internal combustion engines, electromobility is becoming increasingly important. At present, however, there is insufficient infrastructure with regard to charging stations for charging batteries of electric vehicles. Charging stations are available to a small extent just for automobiles. These charging stations have charging connectors that are relatively large and, in particular, are not suitable for charging low-voltage batteries of electrically operated motorcycles or scooters, which provide voltage levels of below 60 V, for example.
Charging a battery or a storage battery of an electrically operated automobile or motorcycle usually requires a special charger that needs to be connected to a safety-ground socket in order to charge the battery of the automobile or motorcycle. However, if there are no sockets available, for example in a car park or in an underground parking garage for a tenant-occupied house or multiple dwelling house, charging the battery of an electrically operated vehicle is often difficult for the driver or associated with increased complexity.
The object of the present invention is to provide an apparatus for providing a supply voltage for operating an electric device of a vehicle, wherein the apparatus provides the supply voltage reliably for a long time. A further object of the present invention is to provide an electrically driven vehicle that can be electrically operated for a long time. A further object of the present invention is to provide a method for providing a supply voltage for operating an electric device of a vehicle in which the supply voltage can be provided reliably for a long time.
An embodiment of an apparatus for providing a supply voltage for operating an electric device of a vehicle includes a supply voltage connection for providing the supply voltage for operating the vehicle, a battery for producing the supply voltage for operating the vehicle, wherein the battery is connected to the supply voltage connection, and a contact-connection device for making contact with a replaceable storage battery for providing a charging voltage for charging the battery. The apparatus additionally includes a coupling device for electrically coupling the replaceable storage battery to the battery, wherein the coupling device is arranged between the contact-connection device and the battery. The coupling device is designed to electrically couple or isolate the replaceable storage battery to/from the battery on the basis of a state of charge of the battery when the replaceable storage battery is in contact with the contact-connection device.
An electrically driven vehicle that can be electrically operated for a long time includes the apparatus specified above for providing a supply voltage for operating an electric device of the vehicle. An electric motor of the vehicle for driving the vehicle, a generator of the vehicle and/or a DC-DC voltage converter of the vehicle may be connected to the supply voltage connection.
A method for providing a supply voltage for operating an electric device of a vehicle provides for the provision of an apparatus for providing a supply voltage for operating the electric device of the vehicle having a battery for producing the supply voltage and a replaceable storage battery for producing a charging voltage for charging the battery. The replaceable storage battery is coupled to the battery when the level of the supply voltage provided by the battery is less than or equal to a first threshold value and the level of the charging voltage produced by the replaceable storage battery is above a second threshold value. The charging voltage of the replaceable storage battery is taken as a basis for producing a charging current that flows into the battery. The replaceable storage battery is isolated from the battery when the level of the supply voltage provided by the battery is above the first threshold value.
Batteries that are used for providing a supply voltage for an electric motor of a vehicle are usually large and heavy, since they need to provide a high drive power, for example a current of 300 A. The batteries or storage batteries permanently installed in electric vehicles weigh up to 20 kg, for example. A contact-connection system for a replaceable storage battery that yields the requisite drive power of 300 A, for example, is likewise large and expensive.
The invention therefore proposes providing the battery that needs to provide the high power as a battery that is permanently fitted in the apparatus for providing the supply voltage and using a small, lightweight and inexpensive storage battery for the replaceable storage battery. The cells of the replaceable storage battery for producing the charging voltage for charging the permanently fitted battery may be optimized for a high energy density, while the permanently fitted battery for producing the supply voltage, for example for operating the electric motor of the vehicle, has battery cells that are optimized for power.
Whereas the permanently fitted battery needs to be designed for the life of the vehicle, the replaceable storage battery can be designed for a shorter life. Fast regeneration of the cell chemistry in the replaceable storage battery is simple to implement and can increase the added value for a used vehicle. When the battery for providing the supply voltage becomes old and loses energy, it is possible to compensate for the energy loss at least in part with a new replacement storage battery having a higher energy density.
The contact-connection device may be designed such that the replaceable storage battery can easily be removed from the apparatus for providing the supply voltage and replaced by another replaceable storage battery. Exchanging the replaceable storage battery does not require specialist personnel from a workshop. A driver can replace the replaceable storage battery himself in uncomplicated fashion. The use of a replaceable storage battery in the apparatus for providing the supply voltage is possible particularly on account of the decoupling between the battery for producing the supply voltage and the replaceable storage battery. For example, it is possible to use motorcycle storage batteries for the replaceable storage battery, these being produced in large numbers and at a reasonable price.
According to one embodiment of the apparatus for providing the supply voltage, besides the charging of the permanently fixed battery by the replaceable battery, there is provision for energy produced during driving to be used to recharge the permanently fitted battery and/or the rechargeable storage battery following a discharge. When the vehicle travels downhill, for example, the energy recovered in the process can be used by the apparatus for providing the supply voltage in order to charge the permanently fitted battery and/or the replaceable storage battery.
The topology of the apparatus for providing the supply voltage can provide for it to be possible to use a plurality of replaceable storage batteries, which are arranged in different contact-connection devices, for the purpose of charging the permanently installed battery. Appropriate switching elements, which may be fitted in the replaceable storage battery packs, and the coupling device can be used to couple the replaceable storage batteries to the permanently fitted main battery selectively on an alternate basis for the purpose of charging the latter.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.